1. Field of the Invention
This invention relates to an off-photometric-range indicator in exposure meters for cameras whereby when the brightness of the object to be photographed is not consistent with the set photometric range of the photometric circuit such condition is visually indicated to the photographer.
2. Description of the Prior Art
Among the known techniques relating to such indicating devices is a method according to which when the luminous intensity on the light receiving surface of a receptor element becomes higher or lower than a certain preset absolute value, such occurrence is indicated by operation of a luminous element such as luminous diode, as for instance proposed in U.S. Pat. No. 3,810,208. This method, as disclosed in said patent, has the advantage that the structure of the device is simplified as no complicated mechanical arrangement is needed; but, on the other hand, it has a drawback in that extra space is required in which to incorporate a luminous element such as luminous diode which is indispensable in this method, and in some cases, there is further necessitated an extra optical system for guiding the light beams from the luminous element into the view finder. Also, as the luminous element, such as luminous diode, consumes relatively high quantities of power as compared with other circuit parts, the battery is quickly exhausted. This becomes a serious problem, particularly when the camera is kept in storage for a long time. Usually, when a camera is not used, it is placed in a dark place where the ambient light intensity is outside the photometric range of the photometric circuit, so that if the power switch of the warning device is kept on, the luminous element in the warning device remains lighted to consume power wastefully, and this could result in exhaustion of the battery during storage of the camera. In the case of a TTL (through-the-lens) photometric camera, the aforementioned difficulty could occur even if the camera is not placed in a dark place, because the light to the receptor element is shut off if the lens cap is left mounted.
Further, conventional exposure indicators often give false indications to misguide the photographer when the light intensity of the object is outside the set photometric range.